The vast majority of mixed plastics generated by consumers are disposed of in landfills, despite the fact that breakdown of these materials by natural degradation is an extremely long process. The idea of recycling mixed plastics using current technologies is not economically attractive. In addition, challenges of impurities and cross-contamination among the resin types are formidable.
It is possible to incinerate mixed plastics to recover energy. However, it has not been possible to do so in a controlled manner that reduces off-gas pollution to desirable standards. In order to discourage the practice, some regulators in Europe have elected to stipulate that energy from plastic fuel is non-renewable although energy from other waste and biomass fuel is considered renewable.
It is the goal of the present invention to provide a technology that economically converts mixed plastic into a liquid or gaseous low molecular weight fuel without generation of significant air pollution. In performing this invention, users would experience a reduction in landfill burdens together with a new clean burning fuel source and, potentially, valuable chemical co-products at commercial purity levels.
Plastics and municipal solid waste are major obstacles to eventual restoration of contaminated land. The practice of selecting for recycle only a few component types and removing only the most accessible portion reduces prospects for a solution. It is an object of this invention to provide low bulk temperature processing of waste plastics and similar hydrocarbons which is devoid of the generation of toxic off-gases which heretofore has belied an economic solution. It is a further notion that by employing technology of the present invention, waste plastics can be processed at small scale at electric power generators dispersed within various communities. In other words, this technology can be employed for manufacturing oxygenated, low-sulphur fuels to be used in electric power generation from municipal plastic waste. The present invention employs a novel cascade of thermal and non-thermal mechanisms to break down large molecules and to separate sulphur, nitrogen, halogen and metal contaminants. Proprietary catalysts and sensitizers accelerate the reactions. This process is preferably conducted in the absence of elemental oxygen or in a starved oxygen atmosphere (i.e., less than 2%) so that oxygenated pollutants are not emitted. Avoiding incineration and the high temperatures associated with pyrolysis allows high selectivity and formation of favored liquid hydrocarbons with simple removal of some contaminants before combustion to generate process heat and subsequent electric power. By-product solids, carbon and inorganic compounds and catalysts produced by the inventive process are not hazardous and in the main can be reprocessed as renewed sensitizers.